The present invention relates to a cleaning technology For removing a powder deposited on a surface to be cleaned, and More specifically to a cleaning technology for removing, with An image forming method and an apparatus for the same for forming an image on an image forming medium by spraying an electrically charged powder as an image forming substance via a powder control member having powder passage holes thereon towards an image forming medium and selectively making the powder flying towards said recording medium pass through said powder passage holes, powder deposited on a surface of said powder control member.
There has been known an image forming method and an apparatus for the same in which an image forming method called as direct toning or toner projection is employed.
In this image forming method, a voltage based on the image information is applied to the control electrodes placed in a space around slits or minute passage holes provided in the powder control member, charged powder as toner is selectively passed and moved through said powder passage holes to directly inject the toner to an image forming medium such as paper for forming an image.
In an image forming apparatus in which the image forming system as described is employed, when an operation for forming images is continued, sometimes the powder or some foreign material get deposited on a surface of a portion forming the powder passage holes of the powder control member. When the powder or other foreign material get deposited on a surface of the powder control member, jet of the powder flying towards an image forming medium can not be controlled as intended, which results in degradation of the image quality.
To overcome the problem as described above, there have been known various types of cleaning methods as well as cleaning apparatuses for cleaning the surface of the powder control member. For instance, as a cleaning method making use of a mechanical force, there has been known a method in which cleaning is executed by making a rotating brush contact the powder control unit (refer to Japanese Patent Laid-Open Publication No. HEI 3-211064), a method in which cleaning is executed by shaking the powder control member (refer to, for instance, Japanese Patent Laid-Open Publication No. HEI 4-216072), a method in which the powder control member is thermally expanded by heating, and the powder or other foreign material deposited on the member is removed away by making use of deformation of the powder control member (refer to Japanese Patent Laid-Open Publication No. HEI 4-141458), a method in which cleaning is executed by using an air flow (refer to Japanese Patent Laid-Open Publication No. SHO 58-94481, Japanese Patent Laid-Open Publication No. HEI 4-191780, Japanese Patent Laid-Open Publication No. HEI 4-505899, Japanese Patent Laid-Open Publication No. HEI 5-134581), or the like.
As a method in which cleaning is executed by making use of an electromagnetic force, there has been known a method in which an electric field is applied to the charged powder and cleaning is executed by making use of an electrostatic force (a Coulomb force) (refer to Japanese Patent Laid-Open Publication No. SHO 58-96570, Japanese Patent Laid-Open Publication No. SHO 58-104769, Japanese Patent Laid-Open Publication No. SHO 58-104771, Japanese Patent Laid-Open Publication No. SHO 59-188450, Japanese Patent Laid-Open Publication No. SHO 63-123060, Japanese Patent Laid-Open Publication No. HEI 3-168767, Japanese Patent Laid-Open Publication No. HEI 4-269563, Japanese Patent Laid-Open Publication No. HEI 4-329154, Japanese Patent Laid-Open Publication No. HEI 5-138919).
Also there has been known a method in which the cleaning methods described above are combined. For instance, Japanese Patent Laid-Open Publication No. HEI 5-92608 discloses an image forming apparatus using a magnetic toner as powder and comprising a toner carrier belt as a powder carrier and a rear surface electrode plate provided to hold a control grid as a powder control member via a gap, in which a voltage having a polarity reverse to that of toner is applied to the control grid when an image is not being formed, to promote separation of the deposited toner by an electrostatic force, and also the magnetic toner deposited on a surface of the control grid is removed by rubbing a surface of the control grid with a magnetic brush on the toner carrier belt. Further, for instance, Japanese Patent Laid-Open Publication No. HEI 7-117257 discloses a cleaning method in which toner on a mesh electrode is discharged and removed by simultaneously injecting an air flow and ions to the mesh electrode as a powder control member. Further, for instance, Japanese Patent Laid-Open Publication No. HEI 6-234233 discloses a multi-color image generating apparatus with a toner carrier as a powder carrier and a rear section electrode belt as a counter electrode member provided therein so that the powder control member is held therebetween, in which toner deposited on the powder control member is dropped with a hair-formed pad provided on the rear section electrode belt, and the toner is sucked and recovered through through-holes formed on the rear section electrode belt. Furthermore, for instance, Japanese Patent Laid-Open Publication No. HEI 5-286165 discloses an image forming apparatus with a developing brush roller as a powder carrier and a counter electrode member so that an aperture electrode is held therebetween via a gap, in which toner deposited on the electrode is swung away by vibrating the aperture electrode, and the toner swung away is recovered by an electric field onto the developing brush roller.
It has been turned out, however, that there are various defects in the cleaning methods based on the conventional technology as described above. For instance, in the cleaning method using a brush roller as described above, as the brush roller rotates contacting the powder control member, the powder control member may be damaged, or pulled off brush may get deposited on the developing section or on the powder control member to generate an abnormal image. Also in the cleaning method in which the powder control member is vibrated or the powder control member is thermally deformed to shake off powder, again there is a chance that the powder control member may be damaged, and in addition powder on the powder control member can not be completely removed just by vibrating or deforming the powder control member, and a portion of the powder may remain there in the deposited state. Also the cleaning method using an electromagnetic force can be applied only to a powder which can be magnetized, which is disadvantageous.
As a cleaning method in which an excellent cleaning capability even for non-magnetic powder can be realized without damaging the powder control member, there are the cleaning method using an air flow and the cleaning method using an electrostatic force (a Coulomb force).
However, in the cleaning method using an air flow described above, for completely removing the powder deposited on the powder control member, it is necessary to provide a large-sized fan, a large-sized pump or the like, as a source for generating an air flow, which not only causes an increase in the cost but also generates larger noise due to the fan or the like. In a case of the cleaning method in which an air flow and ions are simultaneously blown to a mesh electrode as a powder control member as disclosed in Japanese Patent Laid-Open Publication No. HEI 7-117257, as toner on the mesh electrode is removed being discharged, it can be considered that the excellent cleaning performance can be obtained even if an air flow is set to a weak level, but a corona-generating apparatus for generating ions is required, and the simplicity, which is one of the advantages features of the direct toning method, is lost.
When it is tried to completely clean off the powder deposited on a powder control member with the cleaning method that makes use of an electrostatic force (a Coulomb force), it is necessary to apply a high voltage for forming a cleaning electric field for effecting the electrostatic force to the powder, but if the voltage is made excessively higher, discharging may be generated. When magnetic toner, which can be magnetized from outside, is removed by promoting separation of the magnetic toner on a control grid as a powder control member with an electrostatic force and rubbing the toner with a magnetic brush as disclosed in Japanese Patent Laid-Open Publication No. HEI 5-92608 described above, an amplitude of the electric field for effecting the electrostatic force can be suppressed to a degree where discharging is not generated, but there is a disadvantage that this cleaning method can be applied only to magnetic toner (powder). Also in a case where toner shaken off by vibrating an aperture electrode as a powder control member is recovered with an electric field onto a developing brush roller, there is the possibility to suppress the amplitude of the electric field to a level at which discharging is not generated, but in this case toner (powder) may not be shaken off by means of vibration and may remain there.
In an image forming apparatus comprising a plurality of image forming sections for selectively allowing passage of powder flying towards an image forming medium through powder passage holes of the powder control member for forming a multi-color image or for other purposes, when the powder control member is to be cleaned, the possibility can be considered that a cleaning device is provided for each powder control member, but then a plurality of cleaning devices for the powder control members are required, which results in a disadvantage that the number of parts increase. There has been known a method in which a hair-formed pad as a cleaning member is provided on a rear section electrode belt as a counter electrode member for cleaning the plurality of powder control member and toner deposited on the powder control member is dropped with this hair-formed pad (refer to Japanese Patent Laid-Open Publication No. HEI 6-234233), but the powder control member may be damaged due to rubbing by the hair-formed pad.
It is a first object of the present invention to provide an image forming method for forming an image on an image forming medium by spraying an electrically charged powder as an image forming substance via a powder control member having holes thereon through which the powder can pass towards an image forming medium and selectively allowing passage of the powder flying towards said image forming medium through the. holes according to the image information, in which excellent cleaning capability can be achieved, by combining an air flow with an electrostatic force generated by an electric field, even to non-magnetic powder deposited on a powder control member with a small-sized air flow generating unit as well as with an applied voltage at a level where discharging is not generated, and an apparatus for the same.
It is a second object of the present invention to obtain a cleaning device adapted to the image forming method and apparatus in which excellent cleaning performance can be realized even to non-magnetic powder deposited on a body to be cleaned with a small-sized air flow generating unit as well as keeping the applied voltage at a level where discharging is not generated by combining an air flow with an electrostatic force generated by an electric field.
It is a third object of the present invention to provide an image forming apparatus comprising a plurality units of image forming sections each for forming an image on an image forming medium by controlling a powder as an image forming substance flying towards the recording medium with a powder control member having powder passage holes and control electrodes provided around the powder passage holes, which can realize the excellent cleaning capability for each powder control member, even when using a cleaning device making it possible to clean a powder control member in a non-contact form without giving any damage to the powder control member, with a smaller number of components as compared to the configuration in which a plurality of cleaning devices are provided to powder control members respectively.
It is a fourth object of the present invention to provide an image forming apparatus comprising a plurality units of image forming sections each for forming an image on an image forming medium transferred by a belt member by controlling jet of powder as an image forming substance flying from a powder carrier to a counter electrode member, which can easily clean each powder control member without independently providing a cleaning device dedicated to non-contact cleaning of a powder control member, there by not causing any damage due to rubbing.
To achieve the first object described above, the present invention provides an image forming method for forming an image on an image forming medium by making an electrically charged powder as an image forming substance jet via a powder control member having holes thereof through which the powder can pass towards an image forming medium and selectively allowing passage of the powder flying towards the recording medium through the holes according to the image information; wherein an air flow is generated in a space adjacent to the powder control member and at the same time generating a cleaning electric field in said space for making the powder move away from the powder control member.
In the image forming method according to the above invention, an air flow is generated in a space adjacent to the powder control member, and cleaning is executed by blowing away the powder deposited on the surface of the powder control member. Simultaneously with the cleaning with an air flow, a cleaning electric field for moving the powder away from the powder control member by an electrostatic force, and powder deposited on the surface of the powder control member is separated away from the surface. As described above, by combining an air flow with an electrostatic force, cleaning with an air flow and cleaning with an electrostatic force are executed simultaneously.
To achieve the first object described above, the present invention provides an image forming apparatus for forming an image on an image forming medium by making an electrically charged powder as an image forming substance jet via a powder control member having holes thereon through which the powder can pass towards the image forming medium and selectively allowing passage of the powder flying towards the image forming medium through the holes according to image information; and the image forming apparatus comprises an air flow generating unit for generating an air flow in a space adjacent to said powder control member; a cleaning electric field forming unit for forming a cleaning electric field making the powder move away from the powder control member in the space; and a control unit for controlling generation of an air flow by the air flow generating unit as well as formation of the cleaning electric field by the cleaning electric field forming unit.
In the image forming apparatus according to the above invention, when no image is being formed and an image on an image forming medium is not affected, an air flow is generated in a space adjacent to a powder control member by controlling an air generating unit with a control unit, and powder deposited on the surface of the powder control member is separated from the surface for cleaning. Simultaneously, when cleaning with an air flow, a cleaning electric field for moving powder away from the powder control member with an electrostatic force is generated by controlling the electric field control unit with the control unit, and the powder deposited on the surface of the powder control member is separated from the surface by the cleaning electric field for cleaning. As described above, by combining an air flow with an electrostatic force, cleaning with an air flow and cleaning with an electrostatic force are executed simultaneously.
With the image forming apparatus according to the present invention, the air flow generating unit comprises a counter member for an air flow having an air flow port for sucking or blowing out an air flow to and from said powder control member, and a driving unit for driving said counter member for an air flow so that said air flow port can be positioned at an opposite position close to and facing said powder control member and at an off position away from said powder control member.
In the image forming apparatus according to the above invention, the counter member for an air flow having an air flow port for sucking or blowing out an air flow provided at a position separated away from the powder control member is driven by the driving unit when an image is not being formed; and the air flow port is moved to a position close and opposing to the powder control member. With this movement of the air flow to the opposing position, powder deposited on a surface of the powder control member is removed and cleaned off with an air flow sucked into and blown out from the air flow.
The image forming apparatus according to the present invention comprising a powder carrier for carrying thereon an electrically charged powder as an image forming substance; a counter electrode member arranged at a position opposing to the powder carrier; a jet electric field forming unit for forming a jet electric field making the powder on the powder carrier jet towards the counter electrode member; a powder control member having powder passage holes for controlling jet of the powder from the powder carrier to the counter electrode member between the powder carrier and the outer electrode member and also having a control electrode in a space around each of the powder passage holes; and a power source for applying a voltage to the control electrode according to the image information, and the cleaning electric field forming unit comprises a cleaning electrode provided around the air flow port of the counter member for an air flow and a power source for applying a voltage for forming the cleaning electric field between a cleaning electrode and the control electrode.
In the image forming apparatus according to the above invention, when an image is formed, the electrically charged powder as an image forming substance is flown from the powder carrier to the counter electrode member due to the jet electric field formed by the electric field forming unit. The jet of powder to this counter electrode member is controlled by the powder control member having a control electrode with a voltage applied thereto through the powder passage hole according to image information, and an image is formed on the recording medium by selectively depositing the powder on the recording medium carried to a section between the counter electrode member and the powder control member.
And, when an image is not being formed, by applying a voltage to the cleaning electrode provided around the air flow ports of the counter member for an air flow from a power supply source for cleaning, a cleaning electric field is formed between the cleaning electrode and the control electrode of the powder control member. With this cleaning electric field, the powder deposited on the surface of the powder control member is separated from the surface and is moved towards the air flow or away from the air flow. In association with movement of the powder to or away from a surface of the powder control member, the powder deposited on a surface of the powder control member is removed and cleaned off with an air sucked from or blown out from the air flow.
With the image forming apparatus according to the present invention, the counter electrode member comprises a rotatable cylindrical member with the flow port formed thereon or a belt member and is also used as the counter member for air flow.
In the image forming apparatus according to the above invention, when an image is formed, the air flow port of the counter electrode member formed with a cylindrical member rotatable against the powder control member carrier or a belt member is positioned at a position opposing to a section with no air flow port formed therein, and an electrically charged powder as an image forming substance is flown from the powder carrier to the counter electrode member. The jet of powder towards this counter electrode member is controlled by the powder control member having powder passage holes and a control electrode with a voltage applied thereto according to image information, and an image is formed on the recording medium by selectively depositing the powder on the recording medium carried to a section between the counter electrode member and the powder control member.
When an image is not being formed, the counter electrode member is rotated so that the air flow port formed on the counter electrode member also functioning as the counter member for air flow faces a surface of the powder control member, and the powder deposited on the surface of the powder control member is removed and cleaned off with an air flow sucked through or blown out from the air flow port.
With the image forming apparatus according to the present invention, the cleaning electric field is mainly formed by a voltage applied to the cleaning electrode.
In the image forming apparatus according to the above invention, the cleaning electric field between the cleaning electrode around the air flow port of the counter member for an air flow and the control electrode of the powder control member is formed mainly by a voltage applied to the cleaning electrode, so that an electric potential in the control electrode can be suppressed to a level equal to or below a voltage level durable for components of the electric circuit such as an IC connected to the control electrode.
With the image forming apparatus according to the present invention, the cleaning electric field is an electric field formed by superimposing an alternating electric field to a static electric field.
In the image forming apparatus according to the above invention, a cleaning electric field is formed by superimposing an alternating electric field to a static electric field in a space adjacent to the powder control member, and the powder can easily be separated from the surface of the powder control member by effecting a force causing reciprocal movement of the powder deposited on the powder control member as compared to a case where a cleaning electric field comprising only an static electric field is formed.
With the image forming apparatus according to the present invention, a frequency of the alternating electric field is set to a range higher than 0.5 kHz or lower than 3 kHz.
In the image forming apparatus according to the above invention, a force causing reciprocal movement of powder deposited on the powder control member can be effected more accurately by setting a frequency of an alternating electric field in the cleaning electric field within the specified range as described above.
With image forming apparatus according to the present invention, orientation of the air flow and that of the cleaning electric field are set so that orientation of movement of powder moved by said air flow and that of powder moved by said cleaning electric field are identical.
In the image forming apparatus according to the above invention, movement of the powder moved by the air flow is made identical to that of the powder moved by the cleaning electric field, and the powder moved by the cleaning electric field away from the powder control member is moved by the air flow in the substantially same direction of the air flow.
With the image forming apparatus according to the present invention, a maximum value of the cleaning electric field is set to a value smaller than a discharge start electric field obtained according to a Paschen""s electric discharge curve.
In the image forming apparatus according to the above invention, a maximum value of the cleaning electric field is set to a value smaller than a discharge start electric field obtained according to a Paschen""s electric discharge curve to prevent generation of the cleaning electric field.
With the image forming apparatus according to the present invention, an air pressure difference between an air pressure within the counter member for air flow for sucking or blowing out an air flow to and from the powder control member and the atmospheric pressure is set to less than 15 mm (H2O).
In the image forming apparatus according to the above invention, air pressure different between the air pressure inside the counter member for air flow and atmospheric pressure is set to 15 mm (H2O) or below, so that a low cost fan or the like generating little noises can be used as the air generating unit.
With the image forming apparatus according to the present invention, formation of the cleaning electric field by the cleaning electric field forming unit is started in the state where an air flow has been generated by the air flow generating unit.
In the image forming apparatus according to the above invention, in the state where the air flow has been generated by the air flow generating unit and cleaning of the powder with the air flow is being executed, formation of a cleaning electric field by said cleaning electric field generating unit is started and cleaning by the electric field is added, so that, different from a case where cleaning with the electric field is started in the state where cleaning of powder with an air flow is not executed, because of this, powder is not deposited on a surface of a member constituting the cleaning electric field forming unit such as a counter member for an air flow (counter electrode member).
With the image forming apparatus according to the present invention, a gap between the counter member for air flow when the air flow port is present at the opposite position and the powder control member is set to a value smaller than that when the air flow port is present at the off position.
In the image forming apparatus according to the above invention, a gap between the counter member for an air flow when the air flow port is present at the opposite position and the powder control member is set to a small value, so that cleaning with an air flow can be executed more efficiently as compared to a case where the gap be set to the same value as that when the air flow port is at the off position.
With the image forming apparatus according to the present invention, a gap between the counter member for air flow when the air flow port is at the opposite position and the powder control member is set to less than 0.3 mm.
In the image forming apparatus according to the above invention, by setting the gap to 0.3 mm or less, a smaller air flow generating unit such as a fan or the like for generating a specified air flow provided in a space adjacent to the powder control member can be used, and at the same time a level of a voltage for forming a cleaning electric field in the space can be suppressed to a safe level.
In order to achieve the second object described above, the cleaning device according to the present invention comprises an air flow generating unit for generating an air flow in a space adjacent to a cleaned body; and a cleaning electric field forming unit for forming a cleaning electric field moving the powder off from the cleaned body in the space.
In the cleaning device according to the above invention, an air flow is generated in a space adjacent to a surface to be cleaned, and powder deposited on the surface to be cleaned is separated from the surface for cleaning. Simultaneously with the cleaning with an air flow, a cleaning electric field for moving the powder away from the cleaned surface with an electrostatic force is formed, and the powder deposited on the surface is separated from the surface. As described above, by combining an air flow with an electrostatic force, cleaning with an air flow and that with an electrostatic force are executed simultaneously.
It should be noted that, in the cleaning device according to the above invention, to obtain more excellent cleaning capability, it is preferable to form the cleaning electric field with a voltage in which a DC voltage is superimposed to an AC voltage or to set the frequency of the AC voltage within a range in which excellent cleaning capability can be obtained. Also to more securely prevent the generation of electric discharge due to the cleaning electric field, it is desirable to set a gap between a pair of electrodes with the cleaning electric field generated therebetween, a voltage difference between the electrodes, an air pressure in a space with the cleaning electric field formed therein, or other parameters to a level where electric discharge is not generated according to a Paschen""s curve. Further, to improve the cleaning efficiency more, it is preferable to make orientation of movement of the powder moved with the air flow substantially equal to that of the powder moved by the cleaning electric field.
To achieve the third object described above, the image forming apparatus according to the present invention comprises a plurality of image forming section each forming an image on an image forming medium by making an electrically charged powder as an image forming substance jet via a powder control member having powder passage holes towards the recording medium and selectively allowing passage of said powder flying towards said recording medium through the powder passage hole according to image information, and also having a belt member which can move along image forming positions on the image forming section and a belt driving unit for driving said belt member, and in the image forming apparatus, a cleaning device for cleaning the powder control member is movably provided between a cleaning position opposing to the powder control member and an escaping position off from the image forming position. It should be noted that herein the belt member includes not only a belt member for carrying an image forming medium but also a belt member for temporally carrying an image comprising the powder before transferred to the recording medium as an intermediate image carrier.
In the image forming apparatus according to the above invention, an image can be formed by each image forming section on an image forming medium by moving, when an image is to be formed, the cleaning device for cleaning each powder control member is moved from an image forming position for each image forming section to an escaping position off from the image forming position. And when an image is not being formed, the cleaning device is successively moved to a cleaning position opposing to each powder control member to clean the respective powder control member.
With the image forming apparatus according to the present invention, the cleaning device can move along the belt member and also there is provided a driving unit for moving the cleaning device between the escaping position and the cleaning position.
In the image forming apparatus according to the above invention, when an image is formed, the cleaning device for cleaning the powder control member is driven by the driving unit along the belt member to move the cleaning device from the image forming position to the escaping position off from the image forming position to form an image by each image forming section onto a recording medium. When an image is not being formed, the cleaning device is successively moved by the driving unit along the belt member to a cleaning position opposing to each powder control member to clean each powder control member.
With the image forming apparatus according to the present invention, the cleaning apparatus can be set in the slave state where the cleaning device follows movement of the belt member as well as in the released state where the slave state has been released and, also there is provided a slave state switching unit for switching the cleaning device between the slave state and the released state.
In the image forming apparatus according to the above invention, when an image is not being formed and the cleaning device is moved, a state of the cleaning device is switched by the slave state switching unit to the slave state where the cleaning device follows movement of the belt member, and the cleaning device is successively moved, by diving the belt member, to a cleaning position of the powder control member for each image forming section. When an image is being formed and the cleaning device has been moved to the escaping position, a state of the cleaning device is switched by the slave state switching unit to the slave state released state where the slave state to the belt member has been released, so that the cleaning device does not move from the escaping position irrespective of whether the belt member is driven for forming an image on the recording medium or not.
With the image forming apparatus according to the present invention, the cleaning device comprises a belt turning unit for spanning the belt member over a plurality of rotary bodies and turning a portion of the belt member in a direction reverse to the direction in which the belt member opposes to the powder control member, and a cleaning member arranged in an area around which the belt member turns.
In the image forming apparatus according to the above invention, the cleaning member arranged in the area around which the belt member turns can successively be moved to a cleaning position opposing to a powder control member in each image forming section.
With the image forming apparatus according to the present invention, the rotary bodies for the belt turning unit is also used as the cleaning member.
In the image forming apparatus according to the above invention, the rotary bodies for the belt turning unit is also used as the cleaning member, so that a number of the components is further reduced.
With the image forming apparatus according to the present invention, each of the image forming sections comprises a powder carrier for carrying thereon an electrically charged powder as an image forming substance, a counter electrode member arranged at a position opposing to said powder carrier, a jet electric field forming unit for forming a jet electric field making the powder on the powder carrier jet towards the counter electrode member, a powder control member having powder passage holes for controlling jet of the powder from the powder carrier to the counter electrode member between the powder carrier and the counter electrode member and also having a control electrode in a space around each of the powder passage hole, and the image forming apparatus also having a power source for applying a voltage to the control electrode according to image information, and there is provided in the image forming apparatus, an escaping unit for moving the counter electrode member to an escaping position off from a moving path of said cleaning device.
In the image forming apparatus according to the above invention, when an image is not being formed, the counter electrode member located by the escaping unit at a position opposing to each image forming section is moved from the path through which the cleaning device moves off to the escaping position, so that the cleaning device can be moved more surely to the cleaning position in each image forming section without causing any interference between the cleaning device and the counter electrode member.
With the image forming apparatus according to the present invention with each of the image forming sections comprising a powder carrier for carrying thereon an electrically charged powder as an image forming substance, a counter electrode member arranged at a position opposing to said powder carrier, a jet electric field forming unit for forming a jet electric field making the powder on the powder carrier jet towards the counter electrode member, a powder control member having powder passage holes for controlling jet of the powder from the powder carrier to the counter electrode member between the powder carrier and the counter electrode member and also having a control electrode in a space around each of said powder passage hole, the image forming apparatus also having a power source for applying a voltage to said control electrode according to image formation, the belt unit is formed with a conductive material and is used as a common counter electrode member opposing to each powder carrier.
In the image forming apparatus according to the above invention, when an image is formed, powder on each powder carrier is flown towards the belt member as a common counter electrode member formed with a conductive material.
With the image forming apparatus according to the present invention, a belt unit formed so that the belt member is included therein is provided so that the belt unit can swing around a swinging shaft provided in the side contrary to the escaping position with a cleaning position for the each powder control member therebetween.
In the image forming apparatus according to the above invention, the belt unit formed so that the belt member is included therein is swung around the swinging shaft provided in the side contrary to the escaping position with the cleaning position for the each powder control member provided therebetween, so that the cleaning device for cleaning each powder control member can be moved to the cleaning position without contacting the belt member.
With the image forming apparatus according to the present invention with each of the image forming sections comprising a powder carrier for carrying thereon an electrically charged powder as an image forming substance, a counter electrode member arranged at a position opposing to said powder carrier, a jet electric field forming unit for forming a jet electric field making the powder on the powder carrier jet towards said counter electrode member, a powder control member having powder passage holes for controlling jet of the powder from the powder carrier to the counter electrode member between the powder carrier and the counter electrode member and also having a control electrode in a space around each of said powder passage holes, the image forming apparatus also having a power source for applying a voltage to the control electrode according to image information, the counter electrode member is provided so that it can swing together with the belt unit.
In the image forming apparatus according to the above invention having a counter electrode member provided at a position opposing to a powder carrier, the counter electrode member can be slid together with the belt unit, so that it is possible to secure a path for moving the cleaning device for cleaning each powder control member to the cleaning position without giving any interference to the belt member not to the counter electrode member.
To achieve the fourth object as described above, the image forming apparatus according to the present invention comprising a plurality of image forming sections each comprising a powder carrier for carrying thereon an electrically charged powder as an image forming substance, a counter electrode member arranged at a position opposing to said powder carrier, a jet electric field forming unit for forming a jet electric field making powder on the powder carrier jet towards said counter electrode member, a powder control member having powder passage holes for controlling jet of the powder from the powder carrier to the counter electrode member between the powder carrier and the counter electrode member and also having a control electrode in a space around each of said powder passage holes, the image forming apparatus also having a belt member which can move along the image forming positions in each image forming section, a belt driving unit for driving said belt member, and a power source for applying a voltage to the control electrode according to image information, and in the image forming apparatus, an opening for cleaning is formed in the belt member and the counter electrode member is also used as a cleaning member for cleaning said powder control member via said opening.
In the image forming apparatus according to the above invention, the opening for cleaning formed on the belt member is located at a position opposing to the powder control member, and the powder control member is cleaned via the opening with the counter electrode member used also as a cleaning member.
With the image forming apparatus according to the present invention, a rotary member with a distance from a portion of its periphery used for the cleaning to a center of rotation is longer than a distance from the periphery of the other portion to the center of rotation is used as the counter electrode member, and there is provided a rotating/driving unit for driving the rotary member.
In the image forming apparatus according to the present invention, when an image is not being formed, the powder control member can easily be cleaned by rotating the counter electrode member also used as a cleaning member to locate the outer peripheral surface with a longer distance from a center of rotation of the counter electrode member at a position opposing to the powder control member. And, when an image is formed, interference to the belt member is prevented by rotating the outer peripheral surface with a shorter distance from a center of rotation of the counter electrode member to face the peripheral surface to the powder control member.
With the image forming apparatus according to the present invention, edge of said belt member is reinforced with a reinforcing material.
In the image forming apparatus according to the above invention, edge of the belt member with the opening for cleaning formed thereon is reinforced with a reinforcing material to improve the durability of the belt member.
With the image forming apparatus according to the present invention, edge of the opening of the belt member is reinforced with a reinforcing material.
In the image forming apparatus according to the above invention, edge of the opening of the belt member is reinforced with a reinforcing material to improve durability of the belt member.
With the image forming apparatus according to the present invention, a device for generating an air flow in a space adjacent to the powder control member and also forming a cleaning electric field for moving the powder away from the powder control member when located at a position opposing to the powder control member is used.
In the image forming apparatus according to the above invention, when an image is not being formed and the image on the image forming medium is not affected, the cleaning device is successively located to a position opposing to each powder control member, an air flow is generated in a space adjacent to the powder control section, and the powder deposited on a surface of the powder control member is separated and cleaned off from the surface. Simultaneously with the cleaning with an air flow, a cleaning electric field for moving the powder with an electrostatic force away from the powder control member is formed, and the powder deposited on a surface of the powder control member is separated and cleaned off from the surface. Thus by combining an air flow with an electrostatic force, cleaning with an air flow and that with an electrostatic force are executed simultaneously.